Conversion of dicyclic dihydroterpenes to cyclopentene hydrocarbons and pentamethylene hydrocarbons



Patented May 7, 1946 CONVERSION OF DICYCLIC DIHYDBOTER- PENES T CYCLOPENTENE HYDROCAR- BONS AND PENTAMETHYLENE HYDRO- CARBONS Vladimir N. Ipatiei! and Herman Pines, Riverside,

111., assignors to Universal 011 Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application July 29, 1943, Serial No. 498,566

11 Claims. (C1. 260- 686) The present invention relates to the catalytic conversion of hydrocarbons and more particularly to the treatment of dicyclic hydrocarbons to form monocyclic hydrocarbons having the same empirical formula.

We have discovered that by treating a dicyclic hydrocarbon of the terpene type with a dilute aqueous solution of a hydrolyzable salt or a dilute aqueous solution of a strong acid it is possible to prepare valuable hydrocarbon compounds which may be used as a motor fuel, solvents or raw materials for organic synthesis, perfume manufacture, etc.

One object of our invention is to provide a method for effecting the structural rearrangement of carbon atoms of dicyclic hydrocarbons having at least one strained ring.

A further object of our invention is to furnish a new method of isomerizing cyclic hydrocarbons containing at least one six-member ring into monocyclic hydrocarbons having a five-member Broadly, the present invention relates to the treatment of dicyclic hydrocarbons, having at least one strained ring, with a dilute aqueous solution of a hydrolyzable salt or a dilute aqueous solution of an acid to effect the isomerization of the dicyclic hydrocarbon to a compound having fewer carbon atoms in the ring. 1

According to Baeyers strain theory, if the four bonds of a carbon atom are directed toward the vertices of a regular tetrahedron, each forms an angle of 109 28' with the others. Any deviation from this angle is considered to cause a condition oi strain which i accompanied by a corresponding decrease in stability. This angle size holds true for five and six-member rings but in forming smaller rings or larger rings the angle is much different. Under those conditions the bonds are under tension or are strained, and the compounds are relatively unstable.

In one embodiment, the present invention relates to a process which comprises preparing a monocyclic hydrocarbon having a five-member ring by contacting a dicyclic hydrocarbon containing a six-member ring with a catalyst comprising a dilute aqueous solution of an acidacting salt.

A particular feature of our invention resides in the use of catalytic materials comprising dilute aqueous solutions of-readily hydrolyzable salts such as the halides, phosphates, or sulphates of" aluminum, zinc, cobalt, magnesium, iron, etc; If desired, the free acids can be used in place of the salts.

Hydrocarbons which may be employed in the process will include any dicyclic dlhydroterpene having a ring of six carbon atoms and at least one strained ring of three or four carbon atoms. Examples of charging stocks are the dicyclic dihydroterpenes such as pinane, carane, thuiane, sabinane, etc. The mechanism of the reaction is believed to involve the opening of one of the rings and isomerization of the six-member rin to a five-member ring. The product on hydrogenation yields saturated cyclic hydrocarbons which can be proved to be composed of pentamethylene rings.

The temperature at which the reaction takes place may be varied over a wide range depending u on the particular hydrocarbon charged and the catalyst employed, but will generally be within the range of about to about 500 C. and preferably within the range of about 250 to 400 C.

Pressures employed in the process may vary between atmospheric up to about 500 atmospheres and are preferably from about 15 up to about 350 atmospheres. The catalyst concentration may range from about 0.25% up to about 50% and should preferably be from about 0.5% to about 15%. The amount of catalyst used will depend upon the temperature and type of hydrocarbon treated.

The operation may be carried out either as a batch or continuous process. The reaction mixture is kept under pressure so that the hydrolimit the scope oi! the invention in accordance with the data submitted.

Ewample 138 grams of pinane, 150 cc. of water, and 5 grams of magnesium chloride hexahydrate were placed in a steel rotating'autoclave containing a glass liner. Thevreaction was conducted at a temperature of 350 C. and the maximum pressure developed at this temperature was 230 atmospheresr The product resulting from the reaction was separated from the aqueous solution, washed, dried, and submitted to a high temperature Podbleluiak distillation. The product consisted of hydrocarbons having the following boil ing range:

V. chloride.

but not more than four carbon atoms by subjecting said dicyclic dihydroterpene under superatmospheric pressure and at a temperature of from about 250 C. to about 400 C. to the action of an aqueous'solution of an acid-acting salt of a mineral acid. 6. The process a'sdefined in claim 5 further characterized inthat said salt is magnesium 7. .A process for producing cyclopentene hydrocarbons which comprises subjecting a dicy- Cuts 5 to 8 were hydrogenated, with an absorption of one mol of hydrogen per mol of product. The hydrogenated material had the following physical properties: boiling point 159-16l, n

. (142 0.7889 g The hydrogenated product did not'under'go dehydrogenation when passed over platinized alumina at 275 0., indicating the absence of hexamethylene hydrocarbons. The chemical .behavior and physical constants show that the product before hydrogenation consists of alkylated cyclopentene. 80 per cent of cuts 25 to 28 were found-to contain five-memberrings. By recycling the hydrocarbon material an ultimate yield of over 90 per cent 01. cyclopentene hydrocarbons based on the pinane charged may be obtained.

We claim as our invention:

1. A process for producing alkyl cyclopentenes which comprises subjecting pinane to the action of an aqueous solution otmagnesium chloride at a temperature of from about-150 to about 500 C. to isomerize the pinane into the alkyl cyclopentene.

2. A process for producing cyclopentene hyclic dihydroterpene containing a ring having six carbon atoms and a ring having at least three but not more than four carbon atoms to the action or an aqueous solution of an acid-acting salt of a mineral acid at an isomerizing temperature oi. fromabout 150C. to about 500 C.

'.8. The process as deflned in claim '7 further characterized in that said salt is magnesium chloride. i

9. A process for producing pentamethyiene hydrocarbon's which comprises isomerizing a dicyclic dihydroterpene containing a ring having six carbon atoms and a-ring having at least three but not more than four carbon atoms by subjecting said dicyclic dihydroterpene under superatmospheric pressure and at a temperature of from about 150 C. to about 500 C. to the action vof an acidic aqueous solution containing from about 0.25% to about 50% by weight of an acidacting inorganic compound, thereby forming alkyl cyciopentene hydrocarbons, and, hydrogenating the latter to produce said pentamethyiene hydrocarbons.

drocarbons which comprises isomerizing a dicyclic dihydroterpene containing a ring having six carbon atoms and a ring having at least three but not more than four carbon atoms by subjecting said dicyclic dihydroterpene under supera tmospheric pressure and at a temperature of from about 150 C. to about 500 C. to the action of an acidic aqueous solution containing from about 0.25% to about by weight of an acid-acting inorganic compound.

3. The process as defined in claim 2 further characterized in that said inorganic compound is a mineral acid. I

4. The process as defined in claim 2 further characterized in that said inorganic compound is a salt of a mineral acid.

5. A process for producing cyclopentene hydrocarbons which comprises isomerizing a dicyclic dihydroterpene containing a ring having six carbon atoms and a ring having at least three 10. A process for producing pentamethyiene A hydrocarbons which comprises isomerizing a dicyclic dihydroterpene containing a ring having six carbon atoms and a ring having at least three but not more than four carbon atoms by subjecting said dicyclic dihydroterpene under superatmospheric pressure and at a temperature of' from about 250 C. to about 400 C. to the action of an aqueous solution of an acid-acting salt of amineral acid, thereby forming alkyl cyclopenten'e hydrocarbona'and hydrogenating the latter to produce said pentamethyiene hydrocarbons.

11. A process for producing pentamethyiene hydrocarbons which comprises subjecting a dicyclic dihydroterpene containing a ring having six carbon atoms and a ring having at least three but not more than four carbon atoms to the action of an aqueous solution 01' an acid-acting salt ofv a mineral acid at an isomerizing temperature of from about C. to about 500 C.,

thereby forming alkyi cyclopentene hydrocarbons, and hydrogenating the latter to produce said pentamethyiene hydrocarbons.

- mnmm N. IPATIEFF. HERMAN PINES. 

